Aurélie Ludemann

The role of poly(3,4-ethylenedioxythiophene):poly(styrenesulphonate) as a hole injection layer in a blue-emitting polymer light-emitting diode

The authors study the role of the conducting polymer poly(3,4-ethylenedioxythiophene): poly(styrenesulphonate) (PEDOT:PSS) in determining the transient and steady-state operation of a blue-emitting polymer light-emitting diode. Combining the results from photoemission spectroscopy, time-of-flight photocurrent measurements, and studies on hole-only devices reveals a significant barrier for the injection of holes into the polymer. Simulations with a numerical drift-diffusion model, however, show that the injection currents determined from single-carrier devices cannot account for the rapid transient luminance onset and the efficient steady-state luminance output of the corresponding bipolar light-emitting devices. It is shown that the transient electroluminescence traces measured at different external bias can be well reproduced when assuming the presence of a weak barrier for electron extraction at this interface, which is attributed to electron accumulation at a thin phase-segregated PSS-rich layer at the...

Concepts for solution-processable OLED materials at Merck

Drastic performance increase and accelerated progress in organic light-emitting diodes from solutions are shown using solution-processable small molecules based on the core structures of vacuum-evaporable materials. Systematic modification of small-molecule materials toward better processability from solutions at identical electro-optical properties is shown. This is demonstrated to lead to a significant improvement in the device performance.